1. Field of the Invention
This invention relates to an image formation apparatus such as a copying or duplicating machine having a reciprocally movable member for image formation, and more particularly to a drive control therefor.
2. Description of the Prior Art
In a slit exposure copying machine, an optical system such as a lamp and mirrors or a movable member such as an original document carriage supporting an original document thereon is repetitively moved forward and backward by an electromagnetic clutch or the like a number of times to thereby expose and scan an image of the original.
In such a copying machine, when the movable member is to be stopped at a predetermined position after the termination of the last exposure, it is difficult because of the inertia or the like of the movable member to stop the movable member at the predetermined position simply by cutting off the power supply to the electromagnetic clutch. Particularly, where the movable member is an original carriage, the stop position thereof becomes irregular due to the weight of an original thereon and in addition, the original carriage still moves for a little while after the power supply to the clutch has been cut off, and then stops, thus giving unpleasantness to the operator.
It is known to provide a mechanical stop or the like at the stop position to enable the movable member to be stopped at the predetermined position. However, a complex stop mechanism is necessary to prevent noise or shock which would result from the movable member striking against the mechanical stop.
Further, in a compact copying machine, for example, a copying machine wherein the original carriage is moved from the central portion of the apparatus to one end, whereafter it is moved forward in the other direction to thereby effect exposure and scanning and after the termination thereof, the original carriage is returned and stopped at the central portion, the provision of said stop at the central portion to stop the original carriage at a predetermined position would become a hindrance to the forward exposure movement.
Also, as a simple, position detecting element for the movable member in a reciprocal movement exposure type apparatus, there has heretofore been a combination of a microswitch and a cam or a combination of a light-emitting device and a light-receiving device. However, these have their own functional demerits. First, a microswitch has difficulties in life and cam arrangement accuracy, and the use of a light-receiving device suffers from a problem that it is subject to contamination.
Especially, a non-contact type position detecting device is limited in its sensing range. Consequently, if such a device is used for the detection of the stop position of the aforementioned compact copying machine, the original carriage may be moved to one end of the apparatus past the central stop position. Also, if that detecting device is used for the detection of the exposure start position, it will sometimes be impossible to start the exposure when the movable member for exposure scanning is deviated a little from the position of the detecting device.